The present invention is directed to a polypeptide having xcex2-fructofuranosidase activity which can be obtained by expression of a microbial gene.
Fructofuranosyl-transferred saccharides such as xylosylfructoside and lactosucrose, which have a strong anticariogenic activity and growth promoting activity for bifid bacteria, have recently become desirable substitutes for sucrose in the food and pharmaceutical industries. The fructofuranosyl-transferred saccharides are usually produced using xcex2-fructofuranosidases by contacting the enzymes with sucrose and amylaceous saccharides or lactose as starting materials. xcex2-fructofuranosidases derived from microorganisms of the genera Bacillus and Arthrobacter have been widely used. However, these microorganisms do not produce large quantities of the enzyme, so that it is uneconomical to culture these microorganisms on a large scale for enzyme production.
Great strides have recently been made in recombinant DNA technology. Even an enzyme of which the total amino acid sequence is not know can be obtained with relative ease in a desired amount by preparing a recombinant DNA containing a DNA which encodes the enzyme, introducing the recombinant DNA into microorganisms or plant or animal cells to obtain transformants, and culturing the transformants in nutrient culture media. However, in this case a gene encoding the enzyme must be isolated and the nucleotide sequence decoded. In view of the foregoing, it is urgently required to obtain and sequence a gene which encodes xcex2-fructofuranosidase.
The first object of the present invention is to provide a polypeptide having a xcex2-fructofuranosidase activity which can be easily produced on a large scale using recombinant DNA technology.
The second object of the present invention is to provide a DNA encoding the polypeptide.
The third object of the present invention is to provide a transformant into which the DNA is introduced.
The fourth object of the present invention is to provide a process for producing the polypeptide using the transformant.
The fifth object of the present invention is to provide a method for fructofuranosyl transfer using the polypeptide.
To attain the above objects, the present inventors studied energetically and found a polypeptide having a xcex2-fructofuranosidase activity. The amino acid sequences of SEQ ID Nos: 1 and 2 in whole or in part as a partial amino acid sequence, can be easily obtained in a desired amount by expression of a microbial gene.
The first object of the present invention is achieved by a polypeptide which has xcex2-fructofuranosidase activity and the amino acids sequences of SEQ ID NO:1 or 2 in whole or in part as a partial amino acid sequence, and which can be obtained by the expression of a microbial gene.
The second object of the present invention is attained by a DNA encoding the polypeptide.
The third object of the present invention is achieved by a transformant into which the DNA is introduced.
The fourth object of the present invention is attained by a process for producing the polypeptide comprising the steps of culturing the transformant and collecting the polypeptide produced from the culture.
The fifth object of the present invention is achieved by a method for fructofuranosyl transfer comprising a step of reacting a fructofuranosyl donor with a fructofuranosyl acceptor in the present of the polypeptide.